Enteroviruses belong to the family Picornaviridae. They include about 70 human serotypes, e.g., polioviruses, coxsackieviruses A (COX A1-24), coxsackieviruses B (COX B1-6), echoviruses 1-31, enteroviruses (EV68-71), and enterovirus 72 (hepatitis A).
Genomic sequences among various enteroviruses are well conserved. The virion of an enterovirus consists of a simple virus capsid and a single strand of RNA. The viral genome encodes a polyprotein that is proteolytically processed by host and viral proteases into 11 different mature proteins which are encoded in the following order: NH2-VP4-VP2-VP3-VP1-2A-2B-2C-3A-3B-3C-3D-CO2H. Virology Ed. Field, B. N. 1985. The single-stranded RNA is replicated by viral RNA polymerase. See, e.g., Holland et al. (1982) Science 215: 1576-1585; Ward et al. (1988) J. Virol. 62: 558-562; and La Torre et al. (1990) J. Virol. 64: 664-671.
Enteroviruses primarily enter the body through the alimentary canal. They replicate in the cell lining of the alimentary canal before spreading throughout the body via the blood circulation. Clinical syndromes of enteroviral infections are generally mild. Occasionally, enteroviruses cause serious diseases such as paralytic poliomyelitis, meningitis, or myocarditis.
There is a need to develop compounds which are effective in treating infection by enteroviruses.
The present invention is based on the identification of new compounds for use as a therapeutic agent to treat enteroviral infection.
In one aspect, this invention encompasses pyrazolopyrimidine compounds of formula (A): 
A is (CH2)qxe2x80x94CHRaRb; each of R1 and R2, independently, is hydrogen, halogen, cyano, nitro, or alkyl; or R1 and R2 taken together is (CH2)r; each of R3 and R4, independently, is hydrogen, halogen, cyano, nitro, or alkyl; each of R5, Ra, and Rb, independently, is aryl, aralkyl, or heteroaryl, optionally substituted with halogen, cyano, nitro, alkyl, aryl, aralkyl, heteroaryl, OR, O(O)CR, C(O)R, C(O)OR, C(O)NRRxe2x80x2, SR, S(O)R, S(O)OR, NRRxe2x80x2, NR(O)CRxe2x80x2, NRC(O)ORxe2x80x2, or NRC(O)NRxe2x80x2Rxe2x80x3; each of m, n, o, p, and r, independently, is 0 or 1, and q is 0, 1, or 2; in which each of R, Rxe2x80x2, and Rxe2x80x3, independently, is hydrogen or alkyl, provided that the sum of m, n, o, and p is 1, 2, 3, or 4. Note that the left atom shown in any substituted group described above is closest to the pyrazolopyrimidine ring. Also note that if there are more than one R-containing substituted groups in a pyrazolopyrimidine compound of this invention, the Rs can be the same or different. The same rule applies to other similar situation.
Referring to formula (A), a subset of the pyrazolopyrimidine compounds of this invention are those in which each of R1 and R2 is hydrogen. In some embodiments, the sum of m and p is 1 and the sum of n and o is also 1. In other embodiments, the sum of m and p is 1, and the sum of n and o is 2. In this subset of pyrazolopyrimidine compounds, q can be 0; each of Ra and Rb, independently, can be aryl or heteroaryl; R5 can be phenyl, and each of R3 and R4 can be hydrogen.
Another subset of the pyrazolopyrimidine compounds of this invention are those in which R1 and R2 taken together is (CH2)r, and r is 1. In these embodiments, the sum of m and p can be 1 and the sum of n and o can also be 1; q can be 0; each of Ra and Rb, independently, can be aryl; R5 can be aryl (e.g., phenyl); and each of R3 and R4 can be hydrogen.
In another aspect, this invention encompasses pyrazolopyrimidine compounds of formula (A), wherein A is (CH2)qxe2x80x94Ra; each of R1 and R2, independently is hydrogen, halogen, cyano, nitro, or alkyl; or R1 and R2 taken together is (CH2)r; each of R3 and R4, independently, is hydrogen, halogen, cyano, nitro, or alkyl; R5 is aryl, aralkyl, or heteroaryl, optionally substituted with halogen, cyano, nitro, alkyl, aryl, aralkyl, heteroaryl, OR, O(O)CR, C(O)R, C(O)OR, C(O)NRRxe2x80x2, SR, S(O)R, S(O)OR, NRRxe2x80x2, NR(O)CRxe2x80x2, NRC(O)ORxe2x80x2, or NRC(O)NRxe2x80x2Rxe2x80x3; Ra is aryl, aralkyl, or heteroaryl, optionally substituted with halogen, cyano, nitro, alkyl, aryl, aralkyl, heteroaryl, OR, O(O)CR, C(O)R, C(O)OR, C(O)NRRxe2x80x2, SR, S(O)R, S(O)OR, NRRxe2x80x2, NR(O)CRxe2x80x2, NRC(O)ORxe2x80x2, or NRC(O)NRxe2x80x2Rxe2x80x3; each of m, n, o, p, and r, independently, is 0 or 1; and q is 1; in which each of R, Rxe2x80x2, and Rxe2x80x3, independently, is hydrogen or alkyl, provided that the sum of m, n, o, and p is 1, 2, 3, or 4.
In these compounds, Ra can be heteroaryl (e.g., thienyl), R5 can be aryl (e.g., phenyl), and each of R1 and R2 can be hydrogen. In some embodiments, the sum of m and p is 1 and the sum of n and o is also 1, R5 is phenyl, and each of R3 and R4 is hydrogen.
In a further aspect, this invention encompasses pyrazolopyrimidine compounds of formula (A), wherein A is (CH2)qxe2x80x94Ra; each of R1 and R2, independently, is hydrogen, halogen, cyano, nitro, or alkyl; or R1 and R2 taken together is (CH2)r; each of R3 and R4, independently, is hydrogen, halogen, cyano, nitro, or alkyl; each of R5 and Ra, independently, is aryl, aralkyl, or heteroaryl, optionally substituted with halogen, cyano, nitro, alkyl, aryl, aralkyl, heteroaryl, OR, O(O)CR, C(O)R, C(O)OR, C(O)NRRxe2x80x2, SR, S(O)R, S(O)OR, NRRxe2x80x2, NR(O)CRxe2x80x2, NRC(O)ORxe2x80x2, or NRC(O)NRxe2x80x2Rxe2x80x3; each of m, n, o, p, and r, independently, is 0 or 1; and q is 0 and 2; in which each of R, Rxe2x80x2, and Rxe2x80x3, independently, is hydrogen or alkyl, provided that the sum of m, n, o, and p is 1, 2, 3, or 4.
In these compounds, q can be 0, Ra can be aralkyl (e.g., fluorenyl), R5 can be aryl (e.g., phenyl), and each of R1 and R2 can be hydrogen. In some embodiments, the sum of m and p is 1 and the sum of n and o is also 1, R5 is phenyl, and each of R3 and R4 is hydrogen.
This invention also features a method for treating infection by enteroviruses. The method includes administering to a subject in need thereof an effective amount of a compound of formula (A), wherein A is (CH2)qxe2x80x94CHRaRb or (CH2)qxe2x80x94Ra; each of R1 and R2, independently, is hydrogen, halogen, cyano, nitro, or alkyl; or R1 and R2 taken together is (CH2)r; each of R3 and R4, independently, is hydrogen, halogen, cyano, nitro, or alkyl; each of R5, Ra, and Rb, independently, is aryl, aralkyl, or heteroaryl, optionally substituted with halogen, cyano, nitro, alkyl, aryl, aralkyl, heteroaryl, OR, O(O)CR, C(O)R, C(O)OR, C(O)NRRxe2x80x2, SR, S(O)R, S(O)OR, NRRxe2x80x2, NR(O)CRxe2x80x2, NRC(O)ORxe2x80x2, or NRC(O)NRxe2x80x2Rxe2x80x3; each of m, n, o, p, and r, independently, is 0 or 1; and q is 0, 1, or 2; in which each of R, Rxe2x80x2, and Rxe2x80x3, independently, is hydrogen or alkyl, provided that the sum of m, n, o, and p is 1, 2, 3, or 4.
Alkyl, aralkyl, aryl, or heteroaryl herein refers to both substituted and unsubstituted moieties. The term xe2x80x9csubstituted,xe2x80x9d in turn, refers to one or more substituents (which may be the same or different), each replacing a hydrogen atom. The substitutents may be the same or different from those described above. Examples of substituents include, but are not limited to, halogen, hydroxyl, amino, alkylamino, arylamino, dialkylamino, diarylamino, cyano, nitro, mercapto, carbonyl, carbamido, carbamoyl, carboxyl, thioureido, thiocyanato, sulfonamido, alkyl, alkenyl, alkoxy, aryl, heteroaryl, cycloalkyl, and heterocycloalkyl, wherein alkyl, alkenyl, alkoxy, aryl, heteroaryl, cycloalkyl, and heterocycloalkyl, are optionally substituted with alkyl, aryl, heteroaryl, halogen, hydroxyl, amino, mercapto, cyano, or nitro. The term xe2x80x9calkylxe2x80x9d refers to a linear or branched, saturated or unsaturated C1-C6 hydrocarbon moiety. The term xe2x80x9calkoxyxe2x80x9d refers to a linear or branched, saturated or unsaturated, non-aromatic C1-C10 moiety containing an oxygen radical, such as xe2x80x94OCH3 or xe2x80x94OCHxe2x95x90C2H5. The term xe2x80x9ccycloalkylxe2x80x9d refers to a saturated or unsaturated, non-aromatic C3-C10 cyclic hydrocarbon moiety. The term xe2x80x9cheterocycloalkylxe2x80x9d refers to a saturated or unsaturated, non-aromatic C3-C10 cyclic moiety having at least one ring heteroatom, such as O, N, and S. The term xe2x80x9caralkylxe2x80x9d refers to a moiety in which an alkyl hydrogen atom is replaced by an aryl or heteroaryl group. Examples of aralkyl moieties include, but are not limited to, fluorenyl, carbazolyl, 9,10-dihydroanthracenyl, acridanyl, dibenzosuberanyl, iminodibenzyl, and dibenzosuberenyl. The term xe2x80x9carylxe2x80x9d refers to a hydrocarbon ring system having at least one aromatic ring. Examples of aryl moieties include, but are not limited to, phenyl, naphthyl, anthracenyl, perylenyl, and pyrenyl. The term xe2x80x9cheteroarylxe2x80x9d refers to a hydrocarbon ring system having at least one aromatic ring that contains at least one heteroatom such as O, N, or S. Examples of heteroaryl moieties include, but are not limited to, pyridinyl, carbazolyl, and indolyl.
The pyrazolopyrimidine compounds described above include the compounds themselves, as well as their salts and their prodrugs, if applicable. Such salts, for example, can be formed by interaction between a negatively charged substituent (e.g., carboxylate) on a pyrazolopyrimidine compound and a cation. Suitable cations include, but are not limited to, sodium ion, potassium ion, magnesium ion, calcium ion, and an ammonium cation such as teteramethylammonium ion. Likewise, a positively charged substituent (e.g., amino) can form a salt with a negatively charged counterion. Suitable counterions include, but are not limited to, chloride, bromide, iodide, sulfate, nitrate, phosphate, or acetate. Examples of prodrugs include esters and other pharmaceutically acceptable derivatives, which, upon administration to a subject, are capable of providing pyrazolopyrimidine compounds described above. In addition, some of the pyrazolopyrimidine compounds have one or more asymmetric centers. Such compounds can occur as racemates, racemic mixtures, single enantiomers, individual diastereomers, diastereomeric mixtures.
Also within the scope of this invention is a composition containing one or more of the pyrazolopyrimidine compounds described above for use in treating infection by enterovirus, and the use of such a composition for the manufacture of a medicament for the just-described use.
As used herein, the term xe2x80x9ctreating infectionxe2x80x9d refers to use of one or more pyrazolopyrimidine compounds for preventing or treating infection by enterovirus, or other disease states secondary to enteroviral infection.
Shown below are the structures of exemplary pyrazolopyrimidine compounds, i.e., compounds 1-42: 
Other features, objects, and advantages of the invention will be apparent from the description and from the claims.